1. Field of the Invention
The present invention relates to a driving support device for operating automatic braking so as to avoid a collision between an own vehicle and an obstacle, thereby supporting driving of a driver.
2. Description of the Related Art
Hitherto, for example, as proposed in Japanese Patent Application Laid-open No. 2013-220809, there is a known driving support device including radar sensors installed at a rear right corner and a rear left corner of a vehicle body, and using those sensors to detect an obstacle approaching the own vehicle from a rear lateral region during backward travel of the own vehicle, thereby notifying a driver of the existence of the obstacle. Moreover, there is a known collision avoidance system for operating automatic braking when an obstacle is highly likely to collide with an own vehicle, thereby avoiding the collision of the own vehicle with the obstacle.
Thus, a collision avoidance system (referred to as “rear-end collision avoidance support system”) for using a radar sensor to detect an obstacle approaching an own vehicle from a rear lateral region when the own vehicle is traveling backward, and operating automatic braking when the own vehicle is highly likely to collide with the obstacle, thereby avoiding the collision of the own vehicle with the obstacle, is conceivable. In the rear-end collision avoidance support system, for example, in a case where the own vehicle is exiting backward from a parking lot, the driving of the driver can be supported so as to avoid a collision with another vehicle laterally crossing a rear lateral region of the own vehicle.
However, when the own vehicle approaches a guard rail while traveling backward, the rear-end collision avoidance support system may erroneously determine the guard rail to be another vehicle approaching the own vehicle from the rear lateral region depending on the situation, thereby operating automatic braking. A description is now given of a reason for this.
For example, the rear-end collision avoidance support system is configured to use a radar sensor to transmit an electric wave in the millimeter band (referred to as “millimeter wave”), and receive a reflected wave thereof when an obstacle (3D object) reflecting the millimeter wave exists in a transmission range. In particular, when the obstacle is a metal body, a reflected wave having high signal intensity is received. The radar sensor is configured to generate a signal (beat signal) having a beat frequency acquired by signal processing applied to the transmitted wave and the received wave, set a direction in which an output peak of the beat signal is detected as a direction in which the obstacle exists, and calculate a distance between the radar sensor and the obstacle in this direction. One point of the obstacle is acquired as a detection point based on the direction and distance. An electronic control device including the rear-end collision avoidance support system is configured to acquire the detection point of the obstacle at a predetermined sampling cycle from the radar sensor, and determine a likelihood of the collision of the obstacle with the own vehicle based on a predicted travel route of the obstacle predicted from a transition of the detection point (transition of a relative positional relationship between the own vehicle and the obstacle) and a predicted backward travel route of the own vehicle. The electronic control device is configured to operate the automatic braking when the electronic control device determines that the likelihood of the collision is high.
For example, when, as illustrated in FIG. 4, another vehicle approaches the backward travel route of the own vehicle from the rear lateral region of the own vehicle so as to cross the backward travel route, a detection point SP approaching the backward travel route of the own vehicle is detected by a radar sensor 38. As a result, the automatic braking is operated, and consequently, the collision of the own vehicle with the another vehicle can be prevented.
However, when the own vehicle travels backward while approaching a guard rail (metal body), a detection point detected based on a reflected wave reflected by the guard rail may transition so as to cross the backward travel route of the own vehicle. In this case, the electronic control device erroneously determines the detection point on the guard rail as a detection point of another vehicle approaching the backward travel route of the own vehicle so as to cross the backward travel route.
For example, as illustrated in FIG. 5, when parallel parking is carried out along a guard rail, a detection point SP of the guard rail detected by the radar sensor 38 may move so as to cross the backward travel route of the own vehicle as the own vehicle turns. In this case, the automatic braking is unnecessarily operated during the parallel parking.
Moreover, for example, as illustrated in FIG. 6, when another vehicle passes by the own vehicle while the own vehicle is traveling backward parallel to a guard rail, the millimeter wave transmitted by the radar sensor 38 of the own vehicle may be reflected by the another vehicle, and the reflected wave may be further reflected by the guard rail, to thereby be received by the radar sensor 38. In this case, a detection point SP′ is detected in a direction in which the radar sensor 38 receives the reflected wave. This detection point SP′ appears on an opposite side of the own vehicle with respect to the guard rail. Thus, the transition of the detection point SP′ is determined as another vehicle passing on the opposite side with respect to the guard rail. This determined another vehicle is a ghost vehicle which does not actually exist, and this detection point SP′ is referred to as a ghost detection point SP′. Incidentally, the millimeter wave transmitted by the radar sensor 38 toward the guard rail may be directly reflected by the guard rail, to thereby be received by the radar sensor 38. As a result, the detection point SP of the guard rail and the ghost detection point SP′ are combined, and the detection points SP and SP′ may transition so as to cross the backward travel route of the own vehicle. In this case, the automatic braking is unnecessarily operated during the backward travel of the own vehicle.